1. Field of the Invention
The present invention relates to variable focus lens systems having both automatic and manual focusing means in general, and to such lens systems for photographic cameras, in particular.
2. Description of the Prior Art
Variable focus lens systems having coupled rangefinders, such as those found in certain photographic cameras, are well known in the prior art. The most widely used coupled rangefinder is that of the manually actuated optical type that uses triangulation to determine the distance to the subject to be photographed, which is more commonly referred to as subject distance. Coupled rangefinders that automatically determine subject distance by utilizing radiant or acoustical energy reflected from said subject and then transfer or couple the distance derived by such means to the variable focus lens system of a camera to position said lens system to the correct in-focus position, are also known in the prior art. One such automatic system utilizing reflected acoustical energy is described in U.S. Pat. No. 3,522,764 to BIBER et al.
When utilizing a lens focusing system of the type described in the above-mentioned patent, certain conditions may exist that could render such a focusing system ineffective. For example, an acoustical rangefinder cannot effectively focus the variable focus lens system of a camera on a subject to be photographed if such a subject is separated from the camera by a windowpane, especially if such a pane was in relatively close proximity to said camera and said subject was relatively remote. This problem is briefly mentioned in the above-mentioned BIBER et al. patent at Col. 8, lines 4-6. In such a situation, acoustical energy would be reflected from the windowpane, incorrectly indicating that the subject distance was substantially less than its true distance. This erroneous distance information supplied by the acoustical rangefinder would then cause the variable focus lens system to form an out of focus image at its focal plane which, in the case of a camera, would result in an out of focus photograph. This problem could be avoided if the variable focus lens system or camera having such a system had both manual and automatic focus controls. A manually operated optical type coupled rangefinder, for example, is not rendered ineffective if utilized to focus on a subject through transparent media such as a windowpane.
If a variable focus lens system and, specifically, a variable focus lens system in a photographic camera has both manual and automatic focus controls as mentioned above, wherein said focus controlling means are mechanically coupled to one another in a driving relationship, intentional or unintentional actuation of the manual focus actuating means while automatically focusing said variable focus lens system may interfere with the automatic focus control system's ability to correctly focus said camera and, in addition, such actuation of the manual focus control system may overstress structural components of both focusing systems. Simultaneous actuation of the manual and automatic focus control systems can be avoided if the manual focus actuating means is provided with a protective barrier or cover that impedes access to the manual focus actuating means. Such a cover would have to be displaced before the manual focus system could be actuated which would prevent inadvertent actuation of said focus system.
When a camera having both manual and automatic focus controls is in its manual focus control mode, it would be desirable to be able to deenergize the automatic focus control system, to the greatest extent possible, in order to minimize the electrical power drain from the camera's battery system caused by standby electrical loads in said automatic focus control system. When in the manual mode, most of the power consumed by the automatic focus control system normally serves no useful purpose and unnecessarily shortens camera battery life.
In a variable focus lens system having automatic focus control, it is normally necessary to provide gearing between the actuator in the automatic focus control system and the variable focus lens in order to, for example, transmit the appropriate force to said lens and/or to avoid mechanically overloading said actuator. If a variable focus lens system has both manual and automatic focus control and if said manual and automatic focus controls are mechanically coupled to one another through, for example, a variable focus lens, the inertial and frictional loading provided by the automatic focus actuator through its associated focusing gears may make it difficult to manually focus. It would be desirable if means were provided to automatically remove or uncouple at least a portion of the loading created by said actuator and its associated gearing, to facilitate manual focusing.
In addition, in a folding type camera having both manual and automatic focus controls, it would also be desirable to have the automatic focus control mode automatically selected when such a camera is placed in its stored or fully collapsed state so that further focusing by a camera operator would not be necessary before a camera exposure cycle could be initiated once said camera is subsequently placed in its fully erected or picture taking position. If such a camera remained in its previously selected manual mode when in a fully collapsed or stored state, an out of focus photograph could result from an incorrect assumption that said camera was in its automatic mode.